Issue with the grid @earth_relief_03s

Q&A
1

Hello everyone,

I am trying to plot a map for a small region. Therefore, I include the grid @earth_relief_03s. I set my -R such that it is a multiple of 3 arc seconds. However, my map does not have a good resolution and when I run my script I get this warning:
grdblend [WARNING]: File @N30E130.earth_relief_15s_p.nc has different increments (0.00416666666667/0.00416666666667) than the output grid (0.000833333333333/0.000833333333333) - must resample
grdblend [WARNING]: File @N30E130**.earth_relief_15s**_p.nc coordinates are phase-shifted w.r.t. the output grid - must resample
Why do I get a warning related to the grid earth_relief_15s when I defined the grid @earth_relief_03s?

This is my script:

#!/bin/bash
gmt begin Sakurajima-image png
gmt basemap -R130:28:15/130:51:57/31:27:15/31:47:12 -JM18c -Baf -B+t"Probe" -V
gmt grdimage @earth_relief_03s -I+d
gmt colorbar -DjTC+h+o-0c/19.5c+w8c/0.5c+ml -Ba500+l"Earth relief [m]"
gmt coast -Slightblue -L+w5k+c10N+ab+o4c/1c+u --MAP_SCALE_HEIGHT=8p
gmt inset begin -DjTL+w3c+o0.3c #-F+gwhite+pthin
gmt coast -Rg -JG130.4696/31.7816/3c -Bg -Gwheat -SLightBlue -EJP+gdarkgreen
echo 130.5012 31.394 > frame.gmt
echo 130.8787 31.394 >> frame.gmt
echo 130.8787 31.8763 >> frame.gmt
echo 130.5012 31.8763 >> frame.gmt
echo 130.5012 31.394 >> frame.gmt
gmt plot frame.gmt -W5p,red
gmt inset end
gmt end show

I would appreciate your help!

2

Very likely because your region includes some marine part and the 03s, which are derived from SRTM data, only cover continental areas.

3

Thanks Joaquim for answering. Indeed! My region includes marine part. I tried with the grid @srtm_relief_01s and it looks good! The only problem is the “conflict” at the line of coast:

grafik
grafik725×787 157 KB

Here without -SLightBlue in the command gmt coast […]:

grafik
grafik729×790 171 KB

Could you please tell me how can I change this blue color? How can I assign a different color for the sea region? Which parameter is it?

Thanks in advance!
Best regards!

4

-SLightBlue fills the “sea” region in “lightblue”
-S255/0/0 would fill it in red (RGB format)
-S#ffffff would fill it in white (hex format)
…
GMT support different color formats :slight_smile:

If you aim to change the background directly (from grdimage layer)

I’m not 100%, but this might help : doc / color-parameters

gmt set COLORxxx (for everything)

or

grdimage [...] --COLORxxx (for this layer only)